This invention relates generally to gas testing devices. More particularly, the invention relates to an apparatus for testing a gas drawn from a closed system for the presence of contaminants by passing the gas through a testing tube mounted in the apparatus.
U.S. Pat. No. 4,923,806 (Klodowski, issued May 9, 1990) describes an apparatus for testing refrigerant drawn from a closed system for the presence of contaminants. Briefly summarized, the '806 patent describes a testing apparatus in which a very small flow of refrigerant from a closed system such as an air conditioning or refrigeration system is removed from the system, reduced in pressure to near atmospheric and directed through a testing tube. The testing tube contains reagent chemicals that produce a visual indication of the presence of contaminants in the refrigerant. The testing apparatus has means for connecting the apparatus to the system to be tested, pressure reducing means, means for receiving the inlet end of the tube and sealing means for providing a fluid tight fit between the receiver means and the exterior of the tester tube, a testing tube holder having openings at each end and a central cavity into which a testing tube can be inserted. The testing tube has tapered and sealed ends to isolate the chemicals during shipping and storage.
To conduct a test, the ends of the glass testing tube are broken off, thus establishing an open gas flow path through the tube. The now open ended testing tube is inserted into the apparatus so that its inlet end is seated in the receiver means and sealed by the sealing means. The testing apparatus is then connected to the refrigeration system to be tested and a flow of refrigerant flow established through the apparatus and the installed testing tube. After a predetermined time, the flow is stopped and a visual inspection is made of the condition of the reagent chemicals to determine the presence, if any, of contaminants in the system.
The commercialized embodiment of the testing apparatus described in the '806 patent has proven quite successful. Experience with that embodiment, however, has suggested improvements to the apparatus. The current commercial embodiment does not include any flow indicating means. The extremely small refrigerant flow is audible but, in environments having moderate to high background noise, it is difficult or impossible to hear the sound of the flow. Liquid refrigerant can sometimes form at the exit of the testing tube and drip on to the interior wall of the apparatus, where it evaporates. The thermal stress caused by the evaporating refrigerant has sometimes caused the plastic material of the testing tube holder to crack.